Constant %{Qt:QMAKE_MKSPECS} is empty

1. Go to "Tools" -> "Options..." -> "Build & Run" -> "Kits".
2. Select a kit which contains a Qt version.
3. In "Qt mkspec", type a mkspec.
   Because of QTCREATORBUG-16205 you need to use a different mkspec than the one used to build the Qt version. I used "win32-msvc2015".
4. Click "Apply".
5. Add

   %{Qt:QMAKE_MKSPECS}

   to the name of the kit.
   No characters will be added to the kit's name.

I expected the constant to contain the name entered in step 3.